The present invention relates to a filter-paper insert for making brewed beverages, especially coffee or tea, comprising at least two layers of filter paper, which are connected at a base and at opposite side walls to each other for forming an interior space that can be filled, wherein a plurality of slots are introduced into the filter paper for increasing permeability.
European patent document EP 763 994 discloses a filter for brewed beverages, in which two layers of a fibrous filter material are provided in which pores are introduced. These pores have a small pore width of between 0.1 mm to 0.4 mm, wherein a specific fibre density is provided in a boundary region of the pores. As a result, powder particles such as coffee particles can be retained even in relatively small sizes. It is problematic with respect to these small pores however that also oil molecules are retained which have a size of between 25 to 100 μm. Such oils, especially coffee oils in the coffee beverage, are flavour carriers and the filtering of said oil molecules therefore leads to a decrease in the intensity of the coffee flavour.
European patent document EP 2 067 420 discloses a filter insert made of filter paper, in which perforations are introduced into the filter paper, wherein several regions with different permeability levels are provided. It is also problematic in this case that the small perforations not only filter the powder particles but also large oil molecules as the flavour carriers.
German patent document DE 195 16 800 discloses a filter-paper insert for making aromatic extracts of coffee or tea, in which a plurality of slots is introduced which are formed linearly by incisions. The slots can open depending on the hydrostatic pressure during the brewing process. The opening of the slots by the hydrostatic pressure leads to high permeability, so that the dwell time of the brewed water in the filter-paper insert is relatively short and coffee grounds can reach the coffee extract. Furthermore, the filter-paper insert is evenly permeable over its height with the slots arranged evenly for each unit area, so that different quantities of coffee or tea are brewed with different brewing times.